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WHO Classification of Tumours
Trichofolliculoma
Skin


Definition

Trichofolliculoma (TF) is a rare, benign hamartomatous lesion with follicular differentiation. It preferentially arises in the head and neck region; most tumours are found on the face, particularly around the nose. They present as small (5-10 mm), solitary, well-circumscribed, symmetrical dome-shaped lesions with a smooth surface; a tuft of white hairs emerges from a dilated central ostium. Histologically, TF is characterized by a "Caput Medusae" pattern: large numbers of vellus follicles radiate from a dilated infundibulum. One to several infundibulo-cystic structures which are in continuity with the epidermis occupy the centre of the lesion; the vellus follicles are attached to smaller infundibula which radiate from the walls of these cysts. The follicles are surrounded by a highly fibrocytic stroma, and the whole lesion is embedded in cellular connective tissue. Prominent shrinkage clefts separate the lesion from the adjacent dermis. In all TFs, considerable numbers of Merkel cells can be observed.
Trichofolliculoma occurs over a broad age range (11-77 years). It is an entirely benign lesion; there are no reports of tumour progression or aggressive clinical course

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LeBoit PE, Burg G, Weedon D, Sarasin A (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Skin Tumours
3rd Edition
IARC Press: Lyon 2005



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